var version = navigator.appVersion;

    function showKeyCode(e)
    {
    var keycode =(window.event) ? event.keyCode : e.keyCode;

    if ((version.indexOf('MSIE') != -1))
    {
    if(keycode == 116)
    {
    event.keyCode = 0;
    event.returnValue = false;
    return false;
    }
    }
    else
    {
    if(keycode == 116)
    {
    return false;
    }
    }
    }